1. Field of the Invention
The present invention relates generally to compaction presses, and in particular to a method and an apparatus for compacting explosive materials easily and safely to form miniature charges of optimized density.
2. Description of the Conventional Technology
With the miniaturization of munitions and their components, there is a growing need for technology for reliably fabricating primary charges of increasingly smaller diameters. There exist several methods, for example ink-jet printing and femtosecond laser cutting, by which explosive materials can be formed in small volumes, however there are some drawbacks. Laser cutting methods cannot be used with most materials, including primary explosives, such as, lead azide and lead styphnate, which detonate if irradiated with a laser sufficient for ablating material. (Roos, E., Benterou, J., Lee, R., Roeske, F., & Stuart, B. (2002). Femtosecond laser interaction with energetic materials (Preprint UCRL-JC-145670. pp. 11) Taos, NM: SPIE: International Symposium High-Power Laser Ablation. In addition, ink-jet and other methods leave a charge with less than optimal density.
Miniature rams have been used to compact charges in rigid cavities, however, as the dimensions of the cavity decrease, the rams become more prone to breakage; and variations in diameter and alignment become a greater concern. Also, the technology is difficult to scale as multiple needle-like rams across a broad area are susceptible to skew, bending and breakage due to otherwise small variations in alignment, flatness, and load height of the explosive in the cavities. Tooling of the cavities and rams becomes more difficult and expensive.
A schematic of a prior art ram press 100 is shown in FIG. 1. The press 100 includes a rigid platen 42 with a plurality of cavities 44. The cavities are filled with powdered charge material. The powdered charge material is compacted by a ram 132, one ram per cavity where each ram is typically rigid and not deformable, thus forming the charge 70. The schematic illustrates the position of the rams after compression and retraction of the ram. The multiple rams depend from the press head plate 130 driven by cylinder 140.
In the current art, miniature charges are now on the order of 1 millimeter in diameter and 0.5 millimeters thick. Therefore, the rams used in the prior art apparatus 100 are just under 1 millimeter in diameter, and their margin of error (e.g. tolerance) must be correspondingly small.
Needed are a method and an apparatus to compress small samples of powders, such as primary explosives. The samples can be formed by ink-jet printing and the like, and then compacted easily and safely to form miniature charges of optimized density.